Variable Speed Drive Scaled Signal Output as Follower Drive Speed Reference. Variable Speed Drive analog output as speed reference. Analog Speed reference from VFD. Analog out of VFD is Analog input of second VFD.

Directions:

Enter a master speed command in percent, as whole numbers. Maximum speed is 100%.

Click "Master Line Speed" to enter the command.

Enter a follower speed command in percent, as whole numbers.

Click "Follower Speed Ratio" to enter the command.

The follower in this example, can go from 1% of the master's speed, to 2 times (200%) of the master's speed.

System Basics

This system uses a typical signal output from the master drive, as a speed reference input, to a follower drive. In this system, speed sensing feedback devices are used by each drive to compare the commanded speed with the actual speed. Closed loop control of the error between the actual and set speed provides good speed regulation.

Benefits of this system

Easy to set up a follower drive, providing it has a suitable input capability
Scaling the speed commands of each drive is on board the individual drives.
Good regulation based on the resolution of the output signal.

Drawbacks and Pitfalls of this system

When coordinated control is NOT desired, switching to independent control can be complex.
Scaling of each drive speed can require running product for a considerable time.
The programming of the drives on startup can be complicated.
Troubleshooting speed control of each drive can be difficult.

Basic Bill of Materials for the system shown (excluding power transmission, etc.)

2 vsd's
2 motors
2 speed sensing feedback devices (encoder is shown) Can be motor shaft mounted or machine shaft.

	Easy				Difficult
	1	2	3	4	5
Set up Complexity			X
Troubleshoot Complexity			X
System Operation Flexibility				X

Burhans Research Motor Control Systems
Master Line Speed Command	Follower (Slave) Speed Percent